Fatty acid biosynthesis (or FAB) is an important metabolic process for all living organisms and is used to produce the metabolic precursors for membrane phospholipids in the cell wall. Fatty acids are produced by mammals (using enzyme FAS I) and bacteria (using enzyme FAS II) via substantially different biosynthetic mechanisms, thus improving the possibility of bacteria-specific drug targeting. Indeed, inhibitors that are targeting the several stages of the fatty acid biosynthetic pathway have been investigated as anti-bacterial agents. Broadly, the biological pathway of saturated fatty acid biosynthesis (FAB) is more or less similar in all organisms, however, the enzymatic biosynthesis systems of fatty acid synthase (FAS) vary considerably with respect to their structural organization. Mammalian fatty acid synthesis (FAS-I) employs a multifunctional enzyme complex in which all enzymatic activities reside on a single polypeptide. In contrast, bacterial fatty acid synthesis (FAS-II) elongation cycle utilizes various distinct monofunctional enzymes with activity related to respective enzyme peptides effecting fatty acid chain elongation and ultimately cell membrane production. Enoyl acyl carrier protein reductase (FabI) is the component of FAS-II which catalyzes the final reaction in the enzymatic sequence. Therefore, there is a considerable scope for the selective inhibition of the bacterial FAS system enzymes by exploring newer anti-bacterial agents.
FabI (a protein enzyme encoded by EnVM gene) acts as an enoyl-ACP reductase (Bergler, et al, J. Biol. Chem. 269, 1994, 5493-5496) in the final step of the reactions which are involved in each cycle of bacterial fatty acid biosynthesis. Further rounds of this cycle, adding two carbon atoms per cycle, eventually lead to palmitoyl-ACP (16-Carbon), and subsequently the feedback inhibition of FabI by palmitoyl-ACP largely blocks the cycle (Heath et al, J. Biol. Chem. 271, 1996, 1833-1836).

Thus, FabI is one among the major biosynthetic enzyme and appears to be a key moderator in the overall bacterial fatty acid biosynthetic pathway. Therefore, FabI may be one of the meaningful target for acquiring anti-bacterial role.
Though there is plethora of literature on FabI, which provides different inhibitors, however, among promising literature, it reveals that diazaborine (an antibiotics) inhibit fatty acid, phospholipid and lipopolysaccharide (LPS) biosynthesis via Fab I as one of the anti-bacterial target. Grassberger et al, in J. Med. Chem. 27, 1984, 947-953 reported derivative of 2b18 (a peptide) possessing non-competitive inhibitory activity of FabI (Bergler et al, J. Biol. Chem. 269, 1994, 5493-5496). Bergler et al, in J. Biol. Chem. 269, 1994, 5493-5496 reported that inhibition of FabI either by diazaborine or by raising the temperature in a FabI temperature sensitive mutant is lethal. These results demonstrate that FabI appears to be essential for the survival of the organism. McMurry et al, in Nature 394, 1998, 531-532 have shown that FabI is also the target for the well known broad spectrum anti-bacterial agent triclosan. Miller W H et al, in J Med Chem.; 45(15), 2002, 3246-56 disclosed aminopyridine-based inhibitors of bacterial enoyl-ACP reductase (FabI). Recent literature including U.S. Pat. No. 7,790,716; U.S. Pat. No. 7,741,339; U.S. Pat. No. 7,557,125; U.S. Pat. No. 7,524,843; U.S. Pat. No. 7,250,424; U.S. Pat. No. 7,049,310; U.S. Pat. No. 6,846,819; U.S. Pat. No. 6,765,005; U.S. Pat. No. 6,762,201; U.S. Pat. No. 6,730,684 and U.S. Pat. No. 6,503,903 also reveals that diverse compounds are known to possess FabI inhibitory activity and have anti-bacterial role, and, therefore, may be useful for the treatment of bacterial infections in mammals, particularly in man.
International patent application WO2013/021051 disclosed piperidinyl substituted 3,4-dihydro-1H-[1,8]-naphthyridinone derivatives as FabI inhibitors.
Further antimicrobial resistances among clinical isolates have been observed as one of the major problem in recent years. Of particular concern has been the increasing incidence of methicillin-resistant Staphylococcus spp., vancomycin-resistant Enterococcus spp., and penicillin-resistant Streptococcus pneumoniae. 
With the rise in number of patients affected by diverse bacterial and related microbial diseases and drug resistance, there appears to be unmet need for newer drugs that can treat such diseases more effectively. There is still need for newer anti-bacterial agents, which may be further useful in a wide variety of bacterial infections and possessing broader spectrum.